The primary objective of this research is to secure more definitive information on the validity of the property of creep in predicting the susceptibility of amalgam restorations to marginal breakdown. Considerable evidence exists that does indicate a positive correlation between that property and the marginal deterioration of clinical restorations. However, the high and low creep alloys used in those studies have differed from each other with respect to composition, particle size and configuration and, undoubtedly, heat treatment. Thus, a number of variables existed in addition to creep and the question arises as to whether the observed relationship between creep and marginal breakdown is valid for amalgam in general or merely coincidental for those systems. Recent work by this laboratory reveals that the creep of certain alloys can be altered markedly by trituration time. Therefore, in this study it is proposed to eliminate the aforementioned variables by placing paired restorations of a single alloy with widely different creep values, achieved by control of trituration time. The restorations will be monitored for marginal discrepancies over a 3 year period. There is no doubt that one of the real problems in research of this nature is the methodology utilized in the evaluation of the clinical restorations. Several procedures have been or are being employed and it is possible that some of the divergent results emanating from different clinical studies stem from differences in the evaluation criteria and technics. Thus, a second objective of this investigation is to assess the evaluation procedures. All of the restorations will be evaluated at each examination period by 7 recognized technics and the results collated.